import 'package:flutter/material.dart';
import 'package:english_words/english_words.dart';
import 'package:hello_world/page1.dart';
import 'package:hello_world/saved.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new RandomWords(),
      theme: new ThemeData(primaryColor: Colors.teal),
    );
  }
}

class RandomWords extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return new RandomWordsState();
  }
}

class RandomWordsState extends State<RandomWords> {
  final _suggestions = <WordPair>[];
  final _saved = new Set<WordPair>();

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('startup hello generator'),
        actions: <Widget>[
          new IconButton(
            icon: new Icon(Icons.list),
            onPressed: _pushSaved,
          )
        ],
      ),
      body: _buildSuggestions(),
    );
  }

  Widget _buildSuggestions() {
    return new ListView.builder(
      padding: const EdgeInsets.all(16.0),
      // 对于每个建议的单词对都会调用一次itemBuilder，然后将单词对添加到ListTile行中
      // 在偶数行，该函数会为单词对添加一个ListTile row.
      // 在奇数行，该行书湖添加一个分割线widget，来分隔相邻的词对。
      // 注意，在小屏幕上，分割线看起来可能比较吃力。
      itemBuilder: (context, i) {
        if (i.isOdd) {
          return new Divider();
        }
        // 语法 "i ~/ 2" 表示i除以2，但返回值是整形（向下取整），比如i为：1, 2, 3, 4, 5
        // 时，结果为0, 1, 1, 2, 2， 这可以计算出ListView中减去分隔线后的实际单词对数量
        final index = i ~/ 2;
        // 如果是建议列表中最后一个单词对
        if (index >= _suggestions.length) {
          _suggestions.addAll(generateWordPairs().take(10));
        }
        return _buildRows(_suggestions[index]);
      },
    );
  }

  Widget _buildRows(WordPair suggestion) {
    final alreadySaved = _saved.contains(suggestion);
    return new ListTile(
      title: new Text(suggestion.asPascalCase,
          style: new TextStyle(fontSize: 18.0, color: Colors.black87)),
      trailing: new Icon(alreadySaved ? Icons.favorite : Icons.favorite_border,
          color: alreadySaved ? Colors.red : null),
      onTap: () {
        setState(() {
          if (alreadySaved) {
            _saved.remove(suggestion);
            _page1();
          } else {
            _saved.add(suggestion);
            _page1();
          }
        });
      },
    );
  }

  void _pushSaved() {
    Navigator.push(context,
        new MaterialPageRoute(builder: (BuildContext context) {
      return new Saved(
        saved: _saved,
        title: 'saved page',
      );
    }));
  }

  void _page1() {
    Navigator.of(context).push(new MaterialPageRoute(builder: (context) {
      return Page1().build(context);
    }));
  }
}
